In modern and future communication systems, device-to-device (D2D) communication constitutes an issue which is currently under study. Typically, in a D2D communication, two or more devices, such as terminals, mobile stations or user equipments, directly communicate with each other without involving a network entity or any network infrastructure, such as a base station or an access node of a cellular communication network. In this regard, it is currently expected that such D2D communication is capable of intercepting the demand for proximity-based applications in modern and future communication systems. Currently, D2D communication is being studied for example in the context of LTE and LTE-A cellular systems.
In the context of D2D communication, aspects such as device discovery, communication link setup, etc. are studied in terms of enhancements of radio-related layers, and system and security aspects, etc. are studied in terms of enhancements of the overall network architecture. As a result, devices shall be enabled to discover each other and potentially communicate directly over the air interface, when this makes sense from a system management point of view, upon appropriate network supervision. Also, such radio-based discovery and communication process shall be coupled with a system architecture and a security architecture that enables operators to retain control of the device behavior, for example which device can emit discovery signals, when and where discovery signals can be emitted, what information discovery signals shall carry, and what devices should do once they discover each other.
Service requirements and use cases for/in proximity device discovery and D2D communication, which shall be supported, are currently under development. In this regard, it is proposed that proximity device discovery and D2D communication shall be supported across cell borders, i.e. in an inter-cell manner.
For/in such inter-cell or cell border crossing proximity device discovery and D2D communication, problems arise from the situation that the devices reside in different cells, i.e. are served by different cells or base stations/access nodes thereof, while it would be beneficial if these devices were served by the same cell or base station/access node thereof, e.g. from a radio resource control (RRC) point of view. Such problems exemplarily involve problems in D2D communication link setup, e.g. a possibility of unnecessary handovers when routing devices, while setting up a D2D communication link.
Accordingly, in terms of proximity device discovery and D2D communication, there is a desire to improve inter-cell device discovery in D2D communication.